1. Technical Field
This disclosure relates to light emitting diodes (LEDs), dimmer controls, flyback controllers, and power factor correction.
2. Description of Related Art
Cold cathode fluorescent lamps have long-since been used in offices and have become popular in the home. Compared to incandescent lamps, their lumens per watt may be very high, saving energy. However, they may require a high voltage AC inverter and may contain toxic mercury.
Light-emitting diodes (LEDs) are also now capable of providing high light output per watt, comparable to cold cathode fluorescent lamps. Unlike cold cathode fluorescent lamps, moreover, they may not require high voltage and do not usually contain mercury.
Driving LEDs from the 110 volt alternating line current that is typically available, however, may be challenging. Unlike incandescent lamps, for example, the intensity of an LED may be proportional to the current which is delivered through it, not the amount of voltage that is applied across it. Thus, circuitry may be needed to convert the line voltage to a constant current. It may also be desirable to configure this circuitry so that it may drive the LED from the output of a conventional dimmer control, such as one that uses a triac.
One approach has been to convert the output of the dimmer control to a constant current using a flyback converter. Changes in the setting of the dimmer control, however, may not cause the intensity of the LEDs to change in a correspondingly linear fashion. The non-linear way in which the human brain perceives changes in intensity, moreover, may accentuate this lack of linearity.